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SPL neutrino spectra

SPL neutrino spectra. Antoine Cazes Université Claude Bernard Lyon-I December 16 th, 2008. Presentation based on the following paper: Campagne, Cazes : Eur Phys J C45:643-657,2006. Increasing the proton energy:. Positive aspect Increase of the pion cross section Increase of the boost

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SPL neutrino spectra

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  1. SPL neutrino spectra Antoine Cazes Université Claude Bernard Lyon-I December 16th, 2008 Presentation based on the following paper: Campagne, Cazes : Eur Phys J C45:643-657,2006

  2. Increasing the proton energy: • Positive aspect • Increase of the pion cross section • Increase of the boost • Negative aspect • Increase of the kaon cross section • Decrease the number of pot (normalization to 4MW) • Optimization is a balance between these arguments • Guide line : • (Dm²  2.5 10-3eV²) • CERN-Fréjus = 130km  En 260 MeV  pp 600 MeV/c

  3. Particle Producion p+ K+ p- K0 K- Ep(GeV) Ep(GeV) • 500 000 protons, Ek < 5GeV • at 2.2GeV : • 0.26 p+/s • 0.8 10-3 K+/s • at 4.5GeV : • 0.32 p+/s • 5.2 10-3 K+/s • at 3.5GeV : • 0.29 p+/s • 2.8 10-3 K+/s

  4. p p p n Simulation steps • Target simulation • horn simulation • designs • tracking • Decay tunnel • geometry • decay simulation • Fluxes at Fréjus

  5. Interaction between proton beam and target. • Simulation done with FLUKA 2002.4 and MARS • Proton beam • Pencil like • Ek=2.2GeV, 3.5GeV, 4.5GeV, 6.5GeV and 8GeV • Target • Liquid mercury • Long : 30cm •  15mm • Normalization: 4MW • 1.1×1016pot/s@2.2GeV • 0.7×1016pot/s@3.5GeV • 106 protons on target have been produced

  6. Kinetic energy (GeV) of pions and kaons p+ 1GeV 2GeV K0 K+ 1GeV 2GeV 1GeV 2GeV

  7. 80 cm p 140 cm 220 cm Horn design • Low energy proton beam (3.5 GeV) • Large transverse momentum for the pions • <qp> = 55° • Target must be inside the horn:

  8. p En 300 MeV pp 800 MeV/c B1 B2 Optimisation of the horn design • Set a toroïdal magnetic field • Send a pion from the target, Stop when it is horizontal. • Repeat with different angles • Design your horn ! x With different proton energy, the horn can be design to produce similar neutrino flux

  9. p Horn simulation • Drawing from the horn built at CERN • Using Geant 3.2.1 • Tracking cuts • µ, hadrons : 100 keV • g, e+, e- : 10 keV • Stepping : • 10mrad in the magnetic field • 100µm and loose less than 1% of Ek in the conductors

  10. Length modify purity L=10m, 20m, 40m and 60m have been tested. 10m40m nm , nm + 50% to 70% ne , ne + 50% to 100% 40m60m nm , nm + 5% ne , ne+ 20% 40m seems better Radius modify acceptance R=1m, 1.5m and 2m have been Tested 1m 2m (L=40) nm , nm +50% ne , ne +50% to 70% 2m seems better Decay Tunnel Parameters This results have been checked on sensitivity to q13 and dCP

  11. Flux computation • Low energy  Small boost  low focusing • Need a high number of events (~1015 evts!!!) • Use probability • Each time a pion, a muon, or a kaon is decayed by Geant, compute the probability for the neutrino to reach the detector • Use this probability as a weight, and fill an histogram with the neutrino energy • Gives neutrino spectrum.

  12. nm d q p+ 1 – b2 1 A m+ P = p a 4p (b cosa -1)2 L2 p Probability method …. Pions • Pion is tracked by Geant • When it decays, The probability for the neutrino to reach the detector is computed: • p+m+nm : (2-body decay) L : distance to detector A : detector surface To reach the detector: d = -a

  13. 1 A 2 1 1 – bm2 P =  4p L2 mm 1 + bmcosqm (bmcosr -1)2 * (f0(x) Pf1(x)cosqm)  * Probability method …. Muons • m+e+nmne • But muons have small decay probability. • for each muon • loop on the phase space (q,f,E) • compute decay probability e-x/gct • if it decays, compute probability for the neutrino to reach the detector : x = 2En/mm • P is the muon polarisation coming from the pion/kaon decay

  14. Probability method …. Kaons • Very few kaons : • kaon produced in the target is duplicated many times: ~100. • Decay using Geant • Choose the decay channel • Probability computed depending on the decay channel • 2 body decay • 3 body decay

  15. from p and m from K0 from K Ekine (GeV) Ekine (GeV) evts/100m2/y Ekine (GeV) Ekine (GeV) Ek=3.5GeV En ~300MeV L = 40m,R=2m Neutrino Flux 100km away p+ focusing

  16. Neutrino flux @ 130km • 3.5GeV Kinetic proton beam • ~800MeV p focusing • ~300MeV neutrinos • 40m decay tunnel length • 2m decay tunnel radius • Flux available for Ek=2.2GeV, 3.5GeV, 4.5GeV, 6.5GeV and 8GeV and two type of focalization system.

  17. Dm223 (eV2) En~260MeV 2.2GeV 3.5GeV 4.5GeV 8GeV 10-3 dCP = 0 sin22q13 10-3 Proton beam energy comparizon 5 year positive focussing 10 years mixte focussing (8y + and 2y -) Campagne, Cazes : Eur Phys J C45:643-657,2006

  18. Conclusion • Choice of the beam energy is delicate • Tools exist to do another simulation • Proton interaction on target should be better with new version of fluka • Shape of the horns is crucial. • Technical feasability should be taken into account...

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